Browsing School of Physics by Author "HEGARTY, JOHN"
Now showing items 1-14 of 14
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All-optical synchronization and multiplication of the frequency of mode-locked signals
HEGARTY, JOHN (IEEE, 1993)We report all-optical synchronized multiplication by rational fractions of the modulation frequency of optical signals in self-pulsing two-section semiconductor laser diodes. The effect is based on the overlap of harmonics ... -
Asymmetric Fabry-Perot device arrays with low insertion loss and high uniformity
HEGARTY, JOHN (IEEE, 1992)We report on arrays of normally ON asymmetric Fabry-Perot modulator (AFPM) devices which exhibit a high degree of uniformity between devices, with a thickness variation across an array of 0.07%. The devices in one array ... -
Calculation of gain?current characteristics in ZnCdSe?ZnSe quantum well structures including many body effects.
DONEGAN, JOHN FRANCIS; HEGARTY, JOHN (American Institute of Physics, 1996)The gain-spontaneous recombination characteristics have been calculated for a 40 ? Zn0.8Cd0.2Se-ZnSe quantum well including many body effects. We examine the effect of the inclusion of the Coulomb enhancement on the gain ... -
Carrier-density dependence of the photoluminescence lifetimes in ZnCdSe/ZnSSe quantum wells at room temperature
DONEGAN, JOHN; HEGARTY, JOHN (1999)Photoluminescence lifetimes have been measured at room temperature as a function of carrier density in ZnCdSe/ZnSSe quantum wells. We show that, at low carrier density (53109?5 31010 cm22), nonradiative recombination ... -
Design and Construction of an Optoelectronic. Crossbar Switch Containing a Terabit per. Second Free-Space Optical Interconnect
HEGARTY, JOHN (1999)THE COMPLETED DETAILED DESIGN AND INITIAL PHASES OF CONSTRUCTION OF AN OPTOELECTRONIC CROSSBAR DEMONSTRATOR ARE PRESENTED. THE EXPERIMENTAL SYSTEM USES HYBRID VERY LARGE SCALE INTEGRATED OPTOELECTRONICS TECHNOLOGY WHEREBY ... -
Effect of Coulomb enhancement on optical gain in (Zn,Cd)Se/ZnSe multiple quantum wells
DONEGAN, JOHN FRANCIS; HEGARTY, JOHN (American Physical Society, 1997)The optical-gain spectra of a 40-? (Zn,Cd)Se/ZnSe multiple quantum well has been measured at various temperatures using a variable-stripe method. By comparison with a gain calculation including many-body effects, we have ... -
Engineering the exciton linewidth in II-VI quantum well structures
DONEGAN, JOHN FRANCIS; HEGARTY, JOHN (SPIE, 1994)The excitonic transition in Il-VI quantum well materials has recently been used as the basis for optical modulators and also as the lasing transition at low temperatures. The central aspect in the use of the exciton ... -
Optical measurement of the ambipolar diffusion length in a ZnCdSe-ZnSe single quantum well
DONEGAN, JOHN FRANCIS; MC CABE, EITHNE MARY; HEGARTY, JOHN (American Institute of Physics, 1997)We describe a straightforward technique for the measurement of carrier diffusion in semiconductors. Using an optical microscope we can spatially image luminescence with a resolution of ~ 500 nm. We measured the ambipolar ... -
Optically pumped ZnCdSe-ZnSe quantum wells
DONEGAN, JOHN; HEGARTY, JOHN (1996)We have measured the gain spectrum of an optically pumped 40A ZnCdSe-ZnSe multiple quantum well. Our calculation, which includes many body effects such as Coulomb enhancement and spectral broadening due to carrier ... -
Quasi-two-dimensional exciton in ZnSe/ZnMgSSe single quantum well
DONEGAN, JOHN FRANCIS; HEGARTY, JOHN (American Physical Society, 1995)We have studied the quasi-two-dimensional exciton in ZnSe/ZnxMg1 ? xSySe1 ? y (x=0.85, y=0.21) single quantum wells (SQWs) by photoluminescence and photoluminescence excitation spectroscopy. Self-consistent calculations ... -
Sampled grating DBR laser as a spectroscopic source in multigas detection at 1.52-1.57um
HEGARTY, JOHN (2001)The first application is reported of multigas sensing using a widely tuneable sampled grating DBR laser with a tuning range 1520⩽?⩽1570 nm. The laser diode consists of four independently biased sections, two sampled ... -
Small-signal analysis of 1.3/spl mu/m microcavity light-emitting diodes
HEGARTY, JOHN (1999)THE MODULATION SPEED OF 1.3-MU M MICROCAVITY LIGHT-EMITTING DIODES (MCLED'S) HAS BEEN MEASURED USING A SMALL-SIGNAL MODULATION ANALYSIS, A SPEED OF 260 MHZ USING A 25-MU M DIAMETER SAMPLE AT CURRENT DENSITY OF 10 KA/CM(2) ... -
A theoretical analysis of optical clock extraction using a self pulsating laser diode.
HEGARTY, JOHN (1999)The potential for using inexpensive compact disc laser diodes as optical clock extraction elements in transparent networks has led to an increase in research into the dynamics of self-pulsating laser diodes. We use a ...